Soft green algae on a stone - how to achieve

So, I am preemptively trying to grow soft green algae on stones for feeding, but I am not having much luck
In my shrimp tank, the stones are nice green and covered, but when I try to replicate it in a bowl on the windowsill, I get some brown clumps in the water, nothing green and on the stone itself.

I tried plant fertilizer, tank fertilizer, I tried replacing the water, not replacing the water, half replacing the water, cant achieve what I want

I saw many articles, but they recommend close bottle and pebbles, not sure why because that is not explained. Is it possible the stone material plays a role in the algae grow? Or should I add crushed spirulina flake in order to promote the growth?

More light and maybe some water movement.